With the explosive increasing of global data traffic, emerging services, representative of which are video and streaming media services, develop rapidly, thereby making dynamic data services with high bandwidth and high quality requirements become a traffic subject of a network, and driving that the network is evolved toward packetization. It can be seen, in term of a transport network, as a result of a network traffic datamation development, a circuit switching network of a traditional Synchronous Digital Hierarchy (SDH) is developed to an SDH-based Multi-Service Transfer Platform (MSTP) having a multi-service access function which is gradually evolved into an existing Packet Transport Network (PTN). Fundamentally, the circuit switching network only provides rigid-pipeline and coarse-granularity switching, which cannot effectively meet dynamic and burst requirements of the data services, and flexible-pipeline and statistical-multiplexing characteristics of a packet switching network well adapt to the data services. However, current packet switching is basically based on processing on an electric layer, which is high in cost and large in energy consumption; along with the rapid increase of traffic, the processing bottlenecks emerge day by day; and the current packet switching is difficult to adapt to demands for high speed, flexibility, low cost and low energy consumption of a future network. An optical network has the advantages of low cost, low energy consumption, high speed and large capacity. However, a traditional optical circuit switching network such as a Wavelength Division Multiplexing (WDM) network and an Optical Transport Network (OTN) is only capable of providing a large-granularity rigid pipeline, is short of flexibility in electric packet switching, and cannot effectively carry the data services.
An OBTN adopts an Optical Burst (OB)-based all optical switching technology, has abilities to provide space optical layer bandwidths as needed by any network nodes and to perform quick scheduling, can achieve dynamic adaption to and good support for various traffic scenarios such as a south-north burst traffic scenario and an east-west burst traffic scenario, can improve the utilization efficiency of resources and the network flexibility, retains the advantages of high speed, large capacity and low cost of an optical layer, and is applied to various network topologies such as star/tree/ring-shaped network topologies. Meanwhile, a data channel and a control channel perform transfer using different wavelengths, such that it is very convenient to separately process a control signal and a data signal.
The OBTN is divided into a timeslot synchronization network and a non-timeslot synchronization network. A packet in the timeslot synchronization network has a fixed length and is transmitted within a fixed timeslot; and the non-timeslot synchronization network is asynchronous, and a packet has a variable length and does not have a concept of timeslots. The disclosure aims at an optical timeslot synchronization network.
In the timeslot synchronization network, timeslots are rotationally distributed on a loop network, and a full-network synchronization solution is required to synchronize timeslot boundaries. The number of the timeslots in the loop network shall be an integer, and if the number of the timeslots in the loop network is not an integer, timeslot overlapping will occur, which causes a collision. In order to facilitate the loop network timeslot synchronization of the OBTN without the timeslot collisions, it is needed to set a loop length to a timeslot length namely an integral multiple of a timeslot length of an OB.
In order that the number of the timeslots on the loop network is an integer, the length of the loop network or the lengths of the timeslots can be changed. Currently, it is usually needed to configure an OB switching network with a Fibre Delay Line (FDL) in order that a loop length reaches a certain fixed length. If the loop length is an integral multiple of the timeslot length, it is needed to achieve a certain relationship between a data frame and a control frame by means of the FDL inside a node, so that the node receives the control frame prior to the data frame by a certain time length. Moreover, it is required that OB packets must be of a fixed length and a guard interval between the OB packets is also of a fixed length. During the configuration of the FDL, a matched optical switch is also needed, which may make the network design complicated; and the control over the length of the FDL is relatively complex, an accurate time length cannot be achieved, certain losses of optical power will be caused, certain difficulties in the timeslot synchronization of the node will be caused, and the network maintenance is not stable enough. These problems make control over the OBTN in construction and operation processes complicated, thereby being bad for achieving a synchronization function and synchronization management.